mutter/cogl/cogl-pipeline-layer-state.c

/*
 * Cogl
 *
 * An object oriented GL/GLES Abstraction/Utility Layer
 *
 * Copyright (C) 2008,2009,2010 Intel Corporation.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see
 * <http://www.gnu.org/licenses/>.
 *
 *
 *
 * Authors:
 *   Robert Bragg <robert@linux.intel.com>
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "cogl-context-private.h"
#include "cogl-pipeline-private.h"
#include "cogl-blend-string.h"
#include "cogl-util.h"
#include "cogl-matrix.h"

#include "string.h"
#if 0
#include "cogl-context-private.h"
#include "cogl-color-private.h"

#endif

/*
 * XXX: consider special casing layer->unit_index so it's not a sparse
 * property so instead we can assume it's valid for all layer
 * instances.
 * - We would need to initialize ->unit_index in
 *   _cogl_pipeline_layer_copy ().
 *
 * XXX: If you use this API you should consider that the given layer
 * might not be writeable and so a new derived layer will be allocated
 * and modified instead. The layer modified will be returned so you
 * can identify when this happens.
 */
CoglPipelineLayer *
_cogl_pipeline_set_layer_unit (CoglPipeline *required_owner,
                               CoglPipelineLayer *layer,
                               int unit_index)
{
  CoglPipelineLayerState change = COGL_PIPELINE_LAYER_STATE_UNIT;
  CoglPipelineLayer *authority =
    _cogl_pipeline_layer_get_authority (layer, change);
  CoglPipelineLayer *new;

  if (authority->unit_index == unit_index)
    return layer;

  new =
    _cogl_pipeline_layer_pre_change_notify (required_owner,
                                            layer,
                                            change);
  if (new != layer)
    layer = new;
  else
    {
      /* If the layer we found is currently the authority on the state
       * we are changing see if we can revert to one of our ancestors
       * being the authority. */
      if (layer == authority &&
          _cogl_pipeline_layer_get_parent (authority) != NULL)
        {
          CoglPipelineLayer *parent =
            _cogl_pipeline_layer_get_parent (authority);
          CoglPipelineLayer *old_authority =
            _cogl_pipeline_layer_get_authority (parent, change);

          if (old_authority->unit_index == unit_index)
            {
              layer->differences &= ~change;
              return layer;
            }
        }
    }

  layer->unit_index = unit_index;

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= change;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }

  return layer;
}

CoglTexture *
_cogl_pipeline_layer_get_texture_real (CoglPipelineLayer *layer)
{
  CoglPipelineLayer *authority =
    _cogl_pipeline_layer_get_authority (layer,
                                        COGL_PIPELINE_LAYER_STATE_TEXTURE_DATA);

  return authority->texture;
}

CoglTexture *
_cogl_pipeline_get_layer_texture (CoglPipeline *pipeline,
                                  int layer_index)
{
  CoglPipelineLayer *layer =
    _cogl_pipeline_get_layer (pipeline, layer_index);
  return _cogl_pipeline_layer_get_texture (layer);
}

static void
_cogl_pipeline_set_layer_texture_target (CoglPipeline *pipeline,
                                         int layer_index,
                                         GLenum target)
{
  CoglPipelineLayerState change = COGL_PIPELINE_LAYER_STATE_TEXTURE_TARGET;
  CoglPipelineLayer *layer;
  CoglPipelineLayer *authority;
  CoglPipelineLayer *new;

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  if (target == authority->target)
    return;

  new = _cogl_pipeline_layer_pre_change_notify (pipeline, layer, change);
  if (new != layer)
    layer = new;
  else
    {
      /* If the original layer we found is currently the authority on
       * the state we are changing see if we can revert to one of our
       * ancestors being the authority. */
      if (layer == authority &&
          _cogl_pipeline_layer_get_parent (authority) != NULL)
        {
          CoglPipelineLayer *parent =
            _cogl_pipeline_layer_get_parent (authority);
          CoglPipelineLayer *old_authority =
            _cogl_pipeline_layer_get_authority (parent, change);

          if (old_authority->target == target)
            {
              layer->differences &= ~change;

              g_assert (layer->owner == pipeline);
              if (layer->differences == 0)
                _cogl_pipeline_prune_empty_layer_difference (pipeline,
                                                             layer);
              goto changed;
            }
        }
    }

  layer->target = target;

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= change;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }

changed:

  _cogl_pipeline_update_blend_enable (pipeline, COGL_PIPELINE_STATE_LAYERS);
}

static void
_cogl_pipeline_set_layer_texture_data (CoglPipeline *pipeline,
                                       int layer_index,
                                       CoglTexture *texture)
{
  CoglPipelineLayerState change = COGL_PIPELINE_LAYER_STATE_TEXTURE_DATA;
  CoglPipelineLayer *layer;
  CoglPipelineLayer *authority;
  CoglPipelineLayer *new;

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  if (authority->texture == texture)
    return;

  new = _cogl_pipeline_layer_pre_change_notify (pipeline, layer, change);
  if (new != layer)
    layer = new;
  else
    {
      /* If the original layer we found is currently the authority on
       * the state we are changing see if we can revert to one of our
       * ancestors being the authority. */
      if (layer == authority &&
          _cogl_pipeline_layer_get_parent (authority) != NULL)
        {
          CoglPipelineLayer *parent =
            _cogl_pipeline_layer_get_parent (authority);
          CoglPipelineLayer *old_authority =
            _cogl_pipeline_layer_get_authority (parent, change);

          if (old_authority->texture == texture)
            {
              layer->differences &= ~change;

              if (layer->texture != NULL)
                cogl_object_unref (layer->texture);

              g_assert (layer->owner == pipeline);
              if (layer->differences == 0)
                _cogl_pipeline_prune_empty_layer_difference (pipeline,
                                                             layer);
              goto changed;
            }
        }
    }

  if (texture != NULL)
    cogl_object_ref (texture);
  if (layer == authority &&
      layer->texture != NULL)
    cogl_object_unref (layer->texture);
  layer->texture = texture;

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= change;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }

changed:

  _cogl_pipeline_update_blend_enable (pipeline, COGL_PIPELINE_STATE_LAYERS);
}

/* A convenience for querying the target of a given texture that
 * notably returns 0 for NULL textures - so we can say that a layer
 * with no associated CoglTexture will have a texture target of 0.
 */
static GLenum
get_texture_target (CoglTexture *texture)
{
  GLuint ignore_handle;
  GLenum gl_target;

  _COGL_RETURN_VAL_IF_FAIL (texture, 0);

  cogl_texture_get_gl_texture (texture, &ignore_handle, &gl_target);

  return gl_target;
}

void
cogl_pipeline_set_layer_texture (CoglPipeline *pipeline,
                                 int layer_index,
                                 CoglTexture *texture)
{
  /* For the convenience of fragend code we separate texture state
   * into the "target" and the "data", and setting a layer texture
   * updates both of these properties.
   *
   * One example for why this is helpful is that the fragends may
   * cache programs they generate and want to re-use those programs
   * with all pipelines having equivalent fragment processing state.
   * For the sake of determining if pipelines have equivalent fragment
   * processing state we don't need to compare that the same
   * underlying texture objects are referenced by the pipelines but we
   * do need to see if they use the same texture targets. Making this
   * distinction is much simpler if they are in different state
   * groups.
   *
   * Note: if a NULL texture is set then we leave the target unchanged
   * so we can avoid needlessly invalidating any associated fragment
   * program.
   */
  if (texture)
    _cogl_pipeline_set_layer_texture_target (pipeline, layer_index,
                                             get_texture_target (texture));
  _cogl_pipeline_set_layer_texture_data (pipeline, layer_index, texture);
}

void
_cogl_pipeline_set_layer_wrap_modes (CoglPipeline        *pipeline,
                                     CoglPipelineLayer   *layer,
                                     CoglPipelineLayer   *authority,
                                     CoglPipelineWrapModeInternal wrap_mode_s,
                                     CoglPipelineWrapModeInternal wrap_mode_t,
                                     CoglPipelineWrapModeInternal wrap_mode_p)
{
  CoglPipelineLayer     *new;
  CoglPipelineLayerState change = COGL_PIPELINE_LAYER_STATE_WRAP_MODES;

  if (authority->wrap_mode_s == wrap_mode_s &&
      authority->wrap_mode_t == wrap_mode_t &&
      authority->wrap_mode_p == wrap_mode_p)
    return;

  new = _cogl_pipeline_layer_pre_change_notify (pipeline, layer, change);
  if (new != layer)
    layer = new;
  else
    {
      /* If the original layer we found is currently the authority on
       * the state we are changing see if we can revert to one of our
       * ancestors being the authority. */
      if (layer == authority &&
          _cogl_pipeline_layer_get_parent (authority) != NULL)
        {
          CoglPipelineLayer *parent =
            _cogl_pipeline_layer_get_parent (authority);
          CoglPipelineLayer *old_authority =
            _cogl_pipeline_layer_get_authority (parent, change);

          if (old_authority->wrap_mode_s == wrap_mode_s &&
              old_authority->wrap_mode_t == wrap_mode_t &&
              old_authority->wrap_mode_p == wrap_mode_p)
            {
              layer->differences &= ~change;

              g_assert (layer->owner == pipeline);
              if (layer->differences == 0)
                _cogl_pipeline_prune_empty_layer_difference (pipeline,
                                                             layer);
              return;
            }
        }
    }

  layer->wrap_mode_s = wrap_mode_s;
  layer->wrap_mode_t = wrap_mode_t;
  layer->wrap_mode_p = wrap_mode_p;

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= change;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }
}

static CoglPipelineWrapModeInternal
public_to_internal_wrap_mode (CoglPipelineWrapMode mode)
{
  return (CoglPipelineWrapModeInternal)mode;
}

static CoglPipelineWrapMode
internal_to_public_wrap_mode (CoglPipelineWrapModeInternal internal_mode)
{
  _COGL_RETURN_VAL_IF_FAIL (internal_mode !=
                        COGL_PIPELINE_WRAP_MODE_INTERNAL_CLAMP_TO_BORDER,
                        COGL_PIPELINE_WRAP_MODE_AUTOMATIC);
  return (CoglPipelineWrapMode)internal_mode;
}

void
cogl_pipeline_set_layer_wrap_mode_s (CoglPipeline *pipeline,
                                     int layer_index,
                                     CoglPipelineWrapMode mode)
{
  CoglPipelineLayerState       change = COGL_PIPELINE_LAYER_STATE_WRAP_MODES;
  CoglPipelineLayer           *layer;
  CoglPipelineLayer           *authority;
  CoglPipelineWrapModeInternal internal_mode =
    public_to_internal_wrap_mode (mode);

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  _cogl_pipeline_set_layer_wrap_modes (pipeline, layer, authority,
                                       internal_mode,
                                       authority->wrap_mode_t,
                                       authority->wrap_mode_p);
}

void
cogl_pipeline_set_layer_wrap_mode_t (CoglPipeline        *pipeline,
                                     int                  layer_index,
                                     CoglPipelineWrapMode mode)
{
  CoglPipelineLayerState       change = COGL_PIPELINE_LAYER_STATE_WRAP_MODES;
  CoglPipelineLayer           *layer;
  CoglPipelineLayer           *authority;
  CoglPipelineWrapModeInternal internal_mode =
    public_to_internal_wrap_mode (mode);

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  _cogl_pipeline_set_layer_wrap_modes (pipeline, layer, authority,
                                       authority->wrap_mode_s,
                                       internal_mode,
                                       authority->wrap_mode_p);
}

/* The rationale for naming the third texture coordinate 'p' instead
   of OpenGL's usual 'r' is that 'r' conflicts with the usual naming
   of the 'red' component when treating a vector as a color. Under
   GLSL this is awkward because the texture swizzling for a vector
   uses a single letter for each component and the names for colors,
   textures and positions are synonymous. GLSL works around this by
   naming the components of the texture s, t, p and q. Cogl already
   effectively already exposes this naming because it exposes GLSL so
   it makes sense to use that naming consistently. Another alternative
   could be u, v and w. This is what Blender and Direct3D use. However
   the w component conflicts with the w component of a position
   vertex.  */
void
cogl_pipeline_set_layer_wrap_mode_p (CoglPipeline        *pipeline,
                                     int                  layer_index,
                                     CoglPipelineWrapMode mode)
{
  CoglPipelineLayerState       change = COGL_PIPELINE_LAYER_STATE_WRAP_MODES;
  CoglPipelineLayer           *layer;
  CoglPipelineLayer           *authority;
  CoglPipelineWrapModeInternal internal_mode =
    public_to_internal_wrap_mode (mode);

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  _cogl_pipeline_set_layer_wrap_modes (pipeline, layer, authority,
                                       authority->wrap_mode_s,
                                       authority->wrap_mode_t,
                                       internal_mode);
}

void
cogl_pipeline_set_layer_wrap_mode (CoglPipeline        *pipeline,
                                   int                  layer_index,
                                   CoglPipelineWrapMode mode)
{
  CoglPipelineLayerState       change = COGL_PIPELINE_LAYER_STATE_WRAP_MODES;
  CoglPipelineLayer           *layer;
  CoglPipelineLayer           *authority;
  CoglPipelineWrapModeInternal internal_mode =
    public_to_internal_wrap_mode (mode);

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  _cogl_pipeline_set_layer_wrap_modes (pipeline, layer, authority,
                                       internal_mode,
                                       internal_mode,
                                       internal_mode);
  /* XXX: I wonder if we should really be duplicating the mode into
   * the 'r' wrap mode too? */
}

/* FIXME: deprecate this API */
CoglPipelineWrapMode
_cogl_pipeline_layer_get_wrap_mode_s (CoglPipelineLayer *layer)
{
  CoglPipelineLayerState change = COGL_PIPELINE_LAYER_STATE_WRAP_MODES;
  CoglPipelineLayer     *authority;

  _COGL_RETURN_VAL_IF_FAIL (_cogl_is_pipeline_layer (layer), FALSE);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  return internal_to_public_wrap_mode (authority->wrap_mode_s);
}

CoglPipelineWrapMode
cogl_pipeline_get_layer_wrap_mode_s (CoglPipeline *pipeline, int layer_index)
{
  CoglPipelineLayer *layer;

  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), FALSE);

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);
  /* FIXME: we shouldn't ever construct a layer in a getter function */

  return _cogl_pipeline_layer_get_wrap_mode_s (layer);
}

/* FIXME: deprecate this API */
CoglPipelineWrapMode
_cogl_pipeline_layer_get_wrap_mode_t (CoglPipelineLayer *layer)
{
  CoglPipelineLayerState change = COGL_PIPELINE_LAYER_STATE_WRAP_MODES;
  CoglPipelineLayer     *authority;

  _COGL_RETURN_VAL_IF_FAIL (_cogl_is_pipeline_layer (layer), FALSE);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  return internal_to_public_wrap_mode (authority->wrap_mode_t);
}

CoglPipelineWrapMode
cogl_pipeline_get_layer_wrap_mode_t (CoglPipeline *pipeline, int layer_index)
{
  CoglPipelineLayer *layer;

  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), FALSE);

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);
  /* FIXME: we shouldn't ever construct a layer in a getter function */

  return _cogl_pipeline_layer_get_wrap_mode_t (layer);
}

CoglPipelineWrapMode
_cogl_pipeline_layer_get_wrap_mode_p (CoglPipelineLayer *layer)
{
  CoglPipelineLayerState change = COGL_PIPELINE_LAYER_STATE_WRAP_MODES;
  CoglPipelineLayer     *authority =
    _cogl_pipeline_layer_get_authority (layer, change);

  return internal_to_public_wrap_mode (authority->wrap_mode_p);
}

CoglPipelineWrapMode
cogl_pipeline_get_layer_wrap_mode_p (CoglPipeline *pipeline, int layer_index)
{
  CoglPipelineLayer *layer;

  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), FALSE);

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  return _cogl_pipeline_layer_get_wrap_mode_p (layer);
}

void
_cogl_pipeline_layer_get_wrap_modes (CoglPipelineLayer *layer,
                                     CoglPipelineWrapModeInternal *wrap_mode_s,
                                     CoglPipelineWrapModeInternal *wrap_mode_t,
                                     CoglPipelineWrapModeInternal *wrap_mode_p)
{
  CoglPipelineLayer *authority =
    _cogl_pipeline_layer_get_authority (layer,
                                        COGL_PIPELINE_LAYER_STATE_WRAP_MODES);

  *wrap_mode_s = authority->wrap_mode_s;
  *wrap_mode_t = authority->wrap_mode_t;
  *wrap_mode_p = authority->wrap_mode_p;
}

gboolean
cogl_pipeline_set_layer_point_sprite_coords_enabled (CoglPipeline *pipeline,
                                                     int layer_index,
                                                     gboolean enable,
                                                     GError **error)
{
  CoglPipelineLayerState       change =
    COGL_PIPELINE_LAYER_STATE_POINT_SPRITE_COORDS;
  CoglPipelineLayer           *layer;
  CoglPipelineLayer           *new;
  CoglPipelineLayer           *authority;

  _COGL_GET_CONTEXT (ctx, FALSE);

  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), FALSE);

  /* Don't allow point sprite coordinates to be enabled if the driver
     doesn't support it */
  if (enable && !cogl_has_feature (ctx, COGL_FEATURE_ID_POINT_SPRITE))
    {
      if (error)
        {
          g_set_error (error, COGL_ERROR, COGL_ERROR_UNSUPPORTED,
                       "Point sprite texture coordinates are enabled "
                       "for a layer but the GL driver does not support it.");
        }
      else
        {
          static gboolean warning_seen = FALSE;
          if (!warning_seen)
            g_warning ("Point sprite texture coordinates are enabled "
                       "for a layer but the GL driver does not support it.");
          warning_seen = TRUE;
        }

      return FALSE;
    }

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, change);

  if (authority->big_state->point_sprite_coords == enable)
    return TRUE;

  new = _cogl_pipeline_layer_pre_change_notify (pipeline, layer, change);
  if (new != layer)
    layer = new;
  else
    {
      /* If the original layer we found is currently the authority on
       * the state we are changing see if we can revert to one of our
       * ancestors being the authority. */
      if (layer == authority &&
          _cogl_pipeline_layer_get_parent (authority) != NULL)
        {
          CoglPipelineLayer *parent =
            _cogl_pipeline_layer_get_parent (authority);
          CoglPipelineLayer *old_authority =
            _cogl_pipeline_layer_get_authority (parent, change);

          if (old_authority->big_state->point_sprite_coords == enable)
            {
              layer->differences &= ~change;

              g_assert (layer->owner == pipeline);
              if (layer->differences == 0)
                _cogl_pipeline_prune_empty_layer_difference (pipeline,
                                                             layer);
              return TRUE;
            }
        }
    }

  layer->big_state->point_sprite_coords = enable;

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= change;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }

  return TRUE;
}

gboolean
cogl_pipeline_get_layer_point_sprite_coords_enabled (CoglPipeline *pipeline,
                                                     int layer_index)
{
  CoglPipelineLayerState       change =
    COGL_PIPELINE_LAYER_STATE_POINT_SPRITE_COORDS;
  CoglPipelineLayer *layer;
  CoglPipelineLayer *authority;

  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), FALSE);

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);
  /* FIXME: we shouldn't ever construct a layer in a getter function */

  authority = _cogl_pipeline_layer_get_authority (layer, change);

  return authority->big_state->point_sprite_coords;
}

gboolean
_cogl_pipeline_layer_texture_target_equal (CoglPipelineLayer *authority0,
                                           CoglPipelineLayer *authority1,
                                           CoglPipelineEvalFlags flags)
{
  return authority0->target == authority1->target;
}

gboolean
_cogl_pipeline_layer_texture_data_equal (CoglPipelineLayer *authority0,
                                         CoglPipelineLayer *authority1,
                                         CoglPipelineEvalFlags flags)
{
  GLuint gl_handle0, gl_handle1;

  cogl_texture_get_gl_texture (authority0->texture, &gl_handle0, NULL);
  cogl_texture_get_gl_texture (authority1->texture, &gl_handle1, NULL);

  return gl_handle0 == gl_handle1;
}

gboolean
_cogl_pipeline_layer_combine_state_equal (CoglPipelineLayer *authority0,
                                          CoglPipelineLayer *authority1)
{
  CoglPipelineLayerBigState *big_state0 = authority0->big_state;
  CoglPipelineLayerBigState *big_state1 = authority1->big_state;
  int n_args;
  int i;

  if (big_state0->texture_combine_rgb_func !=
      big_state1->texture_combine_rgb_func)
    return FALSE;

  if (big_state0->texture_combine_alpha_func !=
      big_state1->texture_combine_alpha_func)
    return FALSE;

  n_args =
    _cogl_get_n_args_for_combine_func (big_state0->texture_combine_rgb_func);
  for (i = 0; i < n_args; i++)
    {
      if ((big_state0->texture_combine_rgb_src[i] !=
           big_state1->texture_combine_rgb_src[i]) ||
          (big_state0->texture_combine_rgb_op[i] !=
           big_state1->texture_combine_rgb_op[i]))
        return FALSE;
    }

  n_args =
    _cogl_get_n_args_for_combine_func (big_state0->texture_combine_alpha_func);
  for (i = 0; i < n_args; i++)
    {
      if ((big_state0->texture_combine_alpha_src[i] !=
           big_state1->texture_combine_alpha_src[i]) ||
          (big_state0->texture_combine_alpha_op[i] !=
           big_state1->texture_combine_alpha_op[i]))
        return FALSE;
    }

  return TRUE;
}

gboolean
_cogl_pipeline_layer_combine_constant_equal (CoglPipelineLayer *authority0,
                                             CoglPipelineLayer *authority1)
{
  return memcmp (authority0->big_state->texture_combine_constant,
                 authority1->big_state->texture_combine_constant,
                 sizeof (float) * 4) == 0 ? TRUE : FALSE;
}

gboolean
_cogl_pipeline_layer_filters_equal (CoglPipelineLayer *authority0,
                                    CoglPipelineLayer *authority1)
{
  if (authority0->mag_filter != authority1->mag_filter)
    return FALSE;
  if (authority0->min_filter != authority1->min_filter)
    return FALSE;

  return TRUE;
}

static gboolean
compare_wrap_mode_equal (CoglPipelineWrapMode wrap_mode0,
                         CoglPipelineWrapMode wrap_mode1)
{
  /* We consider AUTOMATIC to be equivalent to CLAMP_TO_EDGE because
     the primitives code is expected to override this to something
     else if it wants it to be behave any other way */
  if (wrap_mode0 == COGL_PIPELINE_WRAP_MODE_AUTOMATIC)
    wrap_mode0 = COGL_PIPELINE_WRAP_MODE_CLAMP_TO_EDGE;
  if (wrap_mode1 == COGL_PIPELINE_WRAP_MODE_AUTOMATIC)
    wrap_mode1 = COGL_PIPELINE_WRAP_MODE_CLAMP_TO_EDGE;

  return wrap_mode0 == wrap_mode1;
}

gboolean
_cogl_pipeline_layer_wrap_modes_equal (CoglPipelineLayer *authority0,
                                       CoglPipelineLayer *authority1)
{
  if (!compare_wrap_mode_equal (authority0->wrap_mode_s,
                                authority1->wrap_mode_s) ||
      !compare_wrap_mode_equal (authority0->wrap_mode_t,
                                authority1->wrap_mode_t) ||
      !compare_wrap_mode_equal (authority0->wrap_mode_p,
                                authority1->wrap_mode_p))
    return FALSE;

  return TRUE;
}

gboolean
_cogl_pipeline_layer_user_matrix_equal (CoglPipelineLayer *authority0,
                                        CoglPipelineLayer *authority1)
{
  CoglPipelineLayerBigState *big_state0 = authority0->big_state;
  CoglPipelineLayerBigState *big_state1 = authority1->big_state;

  if (!cogl_matrix_equal (&big_state0->matrix, &big_state1->matrix))
    return FALSE;

  return TRUE;
}

gboolean
_cogl_pipeline_layer_point_sprite_coords_equal (CoglPipelineLayer *authority0,
                                                CoglPipelineLayer *authority1)
{
  CoglPipelineLayerBigState *big_state0 = authority0->big_state;
  CoglPipelineLayerBigState *big_state1 = authority1->big_state;

  return big_state0->point_sprite_coords == big_state1->point_sprite_coords;
}

static void
setup_texture_combine_state (CoglBlendStringStatement *statement,
                             CoglPipelineCombineFunc *texture_combine_func,
                             CoglPipelineCombineSource *texture_combine_src,
                             CoglPipelineCombineOp *texture_combine_op)
{
  int i;

  switch (statement->function->type)
    {
    case COGL_BLEND_STRING_FUNCTION_REPLACE:
      *texture_combine_func = COGL_PIPELINE_COMBINE_FUNC_REPLACE;
      break;
    case COGL_BLEND_STRING_FUNCTION_MODULATE:
      *texture_combine_func = COGL_PIPELINE_COMBINE_FUNC_MODULATE;
      break;
    case COGL_BLEND_STRING_FUNCTION_ADD:
      *texture_combine_func = COGL_PIPELINE_COMBINE_FUNC_ADD;
      break;
    case COGL_BLEND_STRING_FUNCTION_ADD_SIGNED:
      *texture_combine_func = COGL_PIPELINE_COMBINE_FUNC_ADD_SIGNED;
      break;
    case COGL_BLEND_STRING_FUNCTION_INTERPOLATE:
      *texture_combine_func = COGL_PIPELINE_COMBINE_FUNC_INTERPOLATE;
      break;
    case COGL_BLEND_STRING_FUNCTION_SUBTRACT:
      *texture_combine_func = COGL_PIPELINE_COMBINE_FUNC_SUBTRACT;
      break;
    case COGL_BLEND_STRING_FUNCTION_DOT3_RGB:
      *texture_combine_func = COGL_PIPELINE_COMBINE_FUNC_DOT3_RGB;
      break;
    case COGL_BLEND_STRING_FUNCTION_DOT3_RGBA:
      *texture_combine_func = COGL_PIPELINE_COMBINE_FUNC_DOT3_RGBA;
      break;
    }

  for (i = 0; i < statement->function->argc; i++)
    {
      CoglBlendStringArgument *arg = &statement->args[i];

      switch (arg->source.info->type)
        {
        case COGL_BLEND_STRING_COLOR_SOURCE_CONSTANT:
          texture_combine_src[i] = COGL_PIPELINE_COMBINE_SOURCE_CONSTANT;
          break;
        case COGL_BLEND_STRING_COLOR_SOURCE_TEXTURE:
          texture_combine_src[i] = COGL_PIPELINE_COMBINE_SOURCE_TEXTURE;
          break;
        case COGL_BLEND_STRING_COLOR_SOURCE_TEXTURE_N:
          texture_combine_src[i] =
            COGL_PIPELINE_COMBINE_SOURCE_TEXTURE0 + arg->source.texture;
          break;
        case COGL_BLEND_STRING_COLOR_SOURCE_PRIMARY:
          texture_combine_src[i] = COGL_PIPELINE_COMBINE_SOURCE_PRIMARY_COLOR;
          break;
        case COGL_BLEND_STRING_COLOR_SOURCE_PREVIOUS:
          texture_combine_src[i] = COGL_PIPELINE_COMBINE_SOURCE_PREVIOUS;
          break;
        default:
          g_warning ("Unexpected texture combine source");
          texture_combine_src[i] = COGL_PIPELINE_COMBINE_SOURCE_TEXTURE;
        }

      if (arg->source.mask == COGL_BLEND_STRING_CHANNEL_MASK_RGB)
        {
          if (statement->args[i].source.one_minus)
            texture_combine_op[i] =
              COGL_PIPELINE_COMBINE_OP_ONE_MINUS_SRC_COLOR;
          else
            texture_combine_op[i] = COGL_PIPELINE_COMBINE_OP_SRC_COLOR;
        }
      else
        {
          if (statement->args[i].source.one_minus)
            texture_combine_op[i] =
              COGL_PIPELINE_COMBINE_OP_ONE_MINUS_SRC_ALPHA;
          else
            texture_combine_op[i] = COGL_PIPELINE_COMBINE_OP_SRC_ALPHA;
        }
    }
}

gboolean
cogl_pipeline_set_layer_combine (CoglPipeline *pipeline,
				 int layer_index,
				 const char *combine_description,
                                 GError **error)
{
  CoglPipelineLayerState state = COGL_PIPELINE_LAYER_STATE_COMBINE;
  CoglPipelineLayer *authority;
  CoglPipelineLayer *layer;
  CoglBlendStringStatement statements[2];
  CoglBlendStringStatement split[2];
  CoglBlendStringStatement *rgb;
  CoglBlendStringStatement *a;
  GError *internal_error = NULL;
  int count;

  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), FALSE);

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, state);

  count =
    _cogl_blend_string_compile (combine_description,
                                COGL_BLEND_STRING_CONTEXT_TEXTURE_COMBINE,
                                statements,
                                &internal_error);
  if (!count)
    {
      if (error)
	g_propagate_error (error, internal_error);
      else
	{
	  g_warning ("Cannot compile combine description: %s\n",
		     internal_error->message);
	  g_error_free (internal_error);
	}
      return FALSE;
    }

  if (statements[0].mask == COGL_BLEND_STRING_CHANNEL_MASK_RGBA)
    {
      _cogl_blend_string_split_rgba_statement (statements,
                                               &split[0], &split[1]);
      rgb = &split[0];
      a = &split[1];
    }
  else
    {
      rgb = &statements[0];
      a = &statements[1];
    }

  /* FIXME: compare the new state with the current state! */

  /* possibly flush primitives referencing the current state... */
  layer = _cogl_pipeline_layer_pre_change_notify (pipeline, layer, state);

  setup_texture_combine_state (rgb,
                               &layer->big_state->texture_combine_rgb_func,
                               layer->big_state->texture_combine_rgb_src,
                               layer->big_state->texture_combine_rgb_op);

  setup_texture_combine_state (a,
                               &layer->big_state->texture_combine_alpha_func,
                               layer->big_state->texture_combine_alpha_src,
                               layer->big_state->texture_combine_alpha_op);

  /* If the original layer we found is currently the authority on
   * the state we are changing see if we can revert to one of our
   * ancestors being the authority. */
  if (layer == authority &&
      _cogl_pipeline_layer_get_parent (authority) != NULL)
    {
      CoglPipelineLayer *parent = _cogl_pipeline_layer_get_parent (authority);
      CoglPipelineLayer *old_authority =
        _cogl_pipeline_layer_get_authority (parent, state);

      if (_cogl_pipeline_layer_combine_state_equal (authority,
                                                    old_authority))
        {
          layer->differences &= ~state;

          g_assert (layer->owner == pipeline);
          if (layer->differences == 0)
            _cogl_pipeline_prune_empty_layer_difference (pipeline,
                                                         layer);
          goto changed;
        }
    }

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= state;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }

changed:

  _cogl_pipeline_update_blend_enable (pipeline, COGL_PIPELINE_STATE_LAYERS);
  return TRUE;
}

void
cogl_pipeline_set_layer_combine_constant (CoglPipeline *pipeline,
				          int layer_index,
                                          const CoglColor *constant_color)
{
  CoglPipelineLayerState state = COGL_PIPELINE_LAYER_STATE_COMBINE_CONSTANT;
  CoglPipelineLayer     *layer;
  CoglPipelineLayer     *authority;
  CoglPipelineLayer     *new;
  float                  color_as_floats[4];

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, state);

  color_as_floats[0] = cogl_color_get_red_float (constant_color);
  color_as_floats[1] = cogl_color_get_green_float (constant_color);
  color_as_floats[2] = cogl_color_get_blue_float (constant_color);
  color_as_floats[3] = cogl_color_get_alpha_float (constant_color);

  if (memcmp (authority->big_state->texture_combine_constant,
              color_as_floats, sizeof (float) * 4) == 0)
    return;

  new = _cogl_pipeline_layer_pre_change_notify (pipeline, layer, state);
  if (new != layer)
    layer = new;
  else
    {
      /* If the original layer we found is currently the authority on
       * the state we are changing see if we can revert to one of our
       * ancestors being the authority. */
      if (layer == authority &&
          _cogl_pipeline_layer_get_parent (authority) != NULL)
        {
          CoglPipelineLayer *parent =
            _cogl_pipeline_layer_get_parent (authority);
          CoglPipelineLayer *old_authority =
            _cogl_pipeline_layer_get_authority (parent, state);
          CoglPipelineLayerBigState *old_big_state = old_authority->big_state;

          if (memcmp (old_big_state->texture_combine_constant,
                      color_as_floats, sizeof (float) * 4) == 0)
            {
              layer->differences &= ~state;

              g_assert (layer->owner == pipeline);
              if (layer->differences == 0)
                _cogl_pipeline_prune_empty_layer_difference (pipeline,
                                                             layer);
              goto changed;
            }
        }
    }

  memcpy (layer->big_state->texture_combine_constant,
          color_as_floats,
          sizeof (color_as_floats));

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= state;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }

changed:

  _cogl_pipeline_update_blend_enable (pipeline, COGL_PIPELINE_STATE_LAYERS);
}

void
_cogl_pipeline_get_layer_combine_constant (CoglPipeline *pipeline,
                                           int layer_index,
                                           float *constant)
{
  CoglPipelineLayerState       change =
    COGL_PIPELINE_LAYER_STATE_COMBINE_CONSTANT;
  CoglPipelineLayer *layer;
  CoglPipelineLayer *authority;

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);
  /* FIXME: we shouldn't ever construct a layer in a getter function */

  authority = _cogl_pipeline_layer_get_authority (layer, change);
  memcpy (constant, authority->big_state->texture_combine_constant,
          sizeof (float) * 4);
}

/* We should probably make a public API version of this that has a
   matrix out-param. For an internal API it's good to be able to avoid
   copying the matrix */
const CoglMatrix *
_cogl_pipeline_get_layer_matrix (CoglPipeline *pipeline, int layer_index)
{
  CoglPipelineLayerState       change =
    COGL_PIPELINE_LAYER_STATE_USER_MATRIX;
  CoglPipelineLayer *layer;
  CoglPipelineLayer *authority;

  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), NULL);

  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  authority = _cogl_pipeline_layer_get_authority (layer, change);
  return &authority->big_state->matrix;
}

void
cogl_pipeline_set_layer_matrix (CoglPipeline *pipeline,
				int layer_index,
                                const CoglMatrix *matrix)
{
  CoglPipelineLayerState state = COGL_PIPELINE_LAYER_STATE_USER_MATRIX;
  CoglPipelineLayer     *layer;
  CoglPipelineLayer     *authority;
  CoglPipelineLayer     *new;

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, state);

  if (cogl_matrix_equal (matrix, &authority->big_state->matrix))
    return;

  new = _cogl_pipeline_layer_pre_change_notify (pipeline, layer, state);
  if (new != layer)
    layer = new;
  else
    {
      /* If the original layer we found is currently the authority on
       * the state we are changing see if we can revert to one of our
       * ancestors being the authority. */
      if (layer == authority &&
          _cogl_pipeline_layer_get_parent (authority) != NULL)
        {
          CoglPipelineLayer *parent =
            _cogl_pipeline_layer_get_parent (authority);
          CoglPipelineLayer *old_authority =
            _cogl_pipeline_layer_get_authority (parent, state);

          if (cogl_matrix_equal (matrix, &old_authority->big_state->matrix))
            {
              layer->differences &= ~state;

              g_assert (layer->owner == pipeline);
              if (layer->differences == 0)
                _cogl_pipeline_prune_empty_layer_difference (pipeline,
                                                             layer);
              return;
            }
        }
    }

  layer->big_state->matrix = *matrix;

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= state;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }
}

/* FIXME: deprecate and replace with
 * cogl_pipeline_get_layer_texture() instead. */
CoglTexture *
_cogl_pipeline_layer_get_texture (CoglPipelineLayer *layer)
{
  _COGL_RETURN_VAL_IF_FAIL (_cogl_is_pipeline_layer (layer), NULL);

  return _cogl_pipeline_layer_get_texture_real (layer);
}

gboolean
_cogl_pipeline_layer_has_user_matrix (CoglPipeline *pipeline,
                                      int layer_index)
{
  CoglPipelineLayer *layer;
  CoglPipelineLayer *authority;

  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  authority =
    _cogl_pipeline_layer_get_authority (layer,
                                        COGL_PIPELINE_LAYER_STATE_USER_MATRIX);

  /* If the authority is the default pipeline then no, otherwise yes */
  return _cogl_pipeline_layer_get_parent (authority) ? TRUE : FALSE;
}

void
_cogl_pipeline_layer_get_filters (CoglPipelineLayer *layer,
                                  CoglPipelineFilter *min_filter,
                                  CoglPipelineFilter *mag_filter)
{
  CoglPipelineLayer *authority =
    _cogl_pipeline_layer_get_authority (layer,
                                        COGL_PIPELINE_LAYER_STATE_FILTERS);

  *min_filter = authority->min_filter;
  *mag_filter = authority->mag_filter;
}

void
_cogl_pipeline_get_layer_filters (CoglPipeline *pipeline,
                                  int layer_index,
                                  CoglPipelineFilter *min_filter,
                                  CoglPipelineFilter *mag_filter)
{
  CoglPipelineLayer *layer;
  CoglPipelineLayer *authority;

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  authority =
    _cogl_pipeline_layer_get_authority (layer,
                                        COGL_PIPELINE_LAYER_STATE_FILTERS);

  *min_filter = authority->min_filter;
  *mag_filter = authority->mag_filter;
}

CoglPipelineFilter
_cogl_pipeline_get_layer_min_filter (CoglPipeline *pipeline,
                                     int layer_index)
{
  CoglPipelineFilter min_filter;
  CoglPipelineFilter mag_filter;

  _cogl_pipeline_get_layer_filters (pipeline, layer_index,
                                    &min_filter, &mag_filter);
  return min_filter;
}

CoglPipelineFilter
_cogl_pipeline_get_layer_mag_filter (CoglPipeline *pipeline,
                                     int layer_index)
{
  CoglPipelineFilter min_filter;
  CoglPipelineFilter mag_filter;

  _cogl_pipeline_get_layer_filters (pipeline, layer_index,
                                    &min_filter, &mag_filter);
  return mag_filter;
}

CoglPipelineFilter
_cogl_pipeline_layer_get_min_filter (CoglPipelineLayer *layer)
{
  CoglPipelineLayer *authority;

  _COGL_RETURN_VAL_IF_FAIL (_cogl_is_pipeline_layer (layer), 0);

  authority =
    _cogl_pipeline_layer_get_authority (layer,
                                        COGL_PIPELINE_LAYER_STATE_FILTERS);

  return authority->min_filter;
}

CoglPipelineFilter
_cogl_pipeline_layer_get_mag_filter (CoglPipelineLayer *layer)
{
  CoglPipelineLayer *authority;

  _COGL_RETURN_VAL_IF_FAIL (_cogl_is_pipeline_layer (layer), 0);

  authority =
    _cogl_pipeline_layer_get_authority (layer,
                                        COGL_PIPELINE_LAYER_STATE_FILTERS);

  return authority->mag_filter;
}

void
cogl_pipeline_set_layer_filters (CoglPipeline      *pipeline,
                                 int                layer_index,
                                 CoglPipelineFilter min_filter,
                                 CoglPipelineFilter mag_filter)
{
  CoglPipelineLayerState state = COGL_PIPELINE_LAYER_STATE_FILTERS;
  CoglPipelineLayer     *layer;
  CoglPipelineLayer     *authority;
  CoglPipelineLayer     *new;

  _COGL_RETURN_IF_FAIL (cogl_is_pipeline (pipeline));

  /* Note: this will ensure that the layer exists, creating one if it
   * doesn't already.
   *
   * Note: If the layer already existed it's possibly owned by another
   * pipeline. If the layer is created then it will be owned by
   * pipeline. */
  layer = _cogl_pipeline_get_layer (pipeline, layer_index);

  /* Now find the ancestor of the layer that is the authority for the
   * state we want to change */
  authority = _cogl_pipeline_layer_get_authority (layer, state);

  if (authority->min_filter == min_filter &&
      authority->mag_filter == mag_filter)
    return;

  new = _cogl_pipeline_layer_pre_change_notify (pipeline, layer, state);
  if (new != layer)
    layer = new;
  else
    {
      /* If the original layer we found is currently the authority on
       * the state we are changing see if we can revert to one of our
       * ancestors being the authority. */
      if (layer == authority &&
          _cogl_pipeline_layer_get_parent (authority) != NULL)
        {
          CoglPipelineLayer *parent =
            _cogl_pipeline_layer_get_parent (authority);
          CoglPipelineLayer *old_authority =
            _cogl_pipeline_layer_get_authority (parent, state);

          if (old_authority->min_filter == min_filter &&
              old_authority->mag_filter == mag_filter)
            {
              layer->differences &= ~state;

              g_assert (layer->owner == pipeline);
              if (layer->differences == 0)
                _cogl_pipeline_prune_empty_layer_difference (pipeline,
                                                             layer);
              return;
            }
        }
    }

  layer->min_filter = min_filter;
  layer->mag_filter = mag_filter;

  /* If we weren't previously the authority on this state then we need
   * to extended our differences mask and so it's possible that some
   * of our ancestry will now become redundant, so we aim to reparent
   * ourselves if that's true... */
  if (layer != authority)
    {
      layer->differences |= state;
      _cogl_pipeline_layer_prune_redundant_ancestry (layer);
    }
}

void
_cogl_pipeline_layer_hash_unit_state (CoglPipelineLayer *authority,
                                      CoglPipelineLayer **authorities,
                                      CoglPipelineHashState *state)
{
  int unit = authority->unit_index;
  state->hash =
    _cogl_util_one_at_a_time_hash (state->hash, &unit, sizeof (unit));
}

void
_cogl_pipeline_layer_hash_texture_target_state (CoglPipelineLayer *authority,
                                                CoglPipelineLayer **authorities,
                                                CoglPipelineHashState *state)
{
  GLenum gl_target = authority->target;

  state->hash =
    _cogl_util_one_at_a_time_hash (state->hash, &gl_target, sizeof (gl_target));
}

void
_cogl_pipeline_layer_hash_texture_data_state (CoglPipelineLayer *authority,
                                              CoglPipelineLayer **authorities,
                                              CoglPipelineHashState *state)
{
  GLuint gl_handle;

  cogl_texture_get_gl_texture (authority->texture, &gl_handle, NULL);

  state->hash =
    _cogl_util_one_at_a_time_hash (state->hash, &gl_handle, sizeof (gl_handle));
}

void
_cogl_pipeline_layer_hash_filters_state (CoglPipelineLayer *authority,
                                         CoglPipelineLayer **authorities,
                                         CoglPipelineHashState *state)
{
  unsigned int hash = state->hash;
  hash = _cogl_util_one_at_a_time_hash (hash, &authority->mag_filter,
                                        sizeof (authority->mag_filter));
  hash = _cogl_util_one_at_a_time_hash (hash, &authority->min_filter,
                                        sizeof (authority->min_filter));
  state->hash = hash;
}

void
_cogl_pipeline_layer_hash_wrap_modes_state (CoglPipelineLayer *authority,
                                            CoglPipelineLayer **authorities,
                                            CoglPipelineHashState *state)
{
  unsigned int hash = state->hash;
  hash = _cogl_util_one_at_a_time_hash (hash, &authority->wrap_mode_s,
                                        sizeof (authority->wrap_mode_s));
  hash = _cogl_util_one_at_a_time_hash (hash, &authority->wrap_mode_t,
                                        sizeof (authority->wrap_mode_t));
  hash = _cogl_util_one_at_a_time_hash (hash, &authority->wrap_mode_p,
                                        sizeof (authority->wrap_mode_p));
  state->hash = hash;
}

void
_cogl_pipeline_layer_hash_combine_state (CoglPipelineLayer *authority,
                                         CoglPipelineLayer **authorities,
                                         CoglPipelineHashState *state)
{
  unsigned int hash = state->hash;
  CoglPipelineLayerBigState *b = authority->big_state;
  int n_args;
  int i;

  hash = _cogl_util_one_at_a_time_hash (hash, &b->texture_combine_rgb_func,
                                        sizeof (b->texture_combine_rgb_func));
  n_args = _cogl_get_n_args_for_combine_func (b->texture_combine_rgb_func);
  for (i = 0; i < n_args; i++)
    {
      hash =
        _cogl_util_one_at_a_time_hash (hash, &b->texture_combine_rgb_src[i],
                                       sizeof (b->texture_combine_rgb_src[i]));
      hash =
        _cogl_util_one_at_a_time_hash (hash, &b->texture_combine_rgb_op[i],
                                       sizeof (b->texture_combine_rgb_op[i]));
    }

  hash = _cogl_util_one_at_a_time_hash (hash, &b->texture_combine_alpha_func,
                                        sizeof (b->texture_combine_alpha_func));
  n_args = _cogl_get_n_args_for_combine_func (b->texture_combine_alpha_func);
  for (i = 0; i < n_args; i++)
    {
      hash =
        _cogl_util_one_at_a_time_hash (hash, &b->texture_combine_alpha_src[i],
                                       sizeof (b->texture_combine_alpha_src[i]));
      hash =
        _cogl_util_one_at_a_time_hash (hash, &b->texture_combine_alpha_op[i],
                                       sizeof (b->texture_combine_alpha_op[i]));
    }

  state->hash = hash;
}

void
_cogl_pipeline_layer_hash_combine_constant_state (CoglPipelineLayer *authority,
                                                  CoglPipelineLayer **authorities,
                                                  CoglPipelineHashState *state)
{
  CoglPipelineLayerBigState *b = authority->big_state;
  gboolean need_hash = FALSE;
  int n_args;
  int i;

  /* XXX: If the user also asked to hash the ALPHA_FUNC_STATE then it
   * would be nice if we could combine the n_args loops in this
   * function and _cogl_pipeline_layer_hash_combine_state.
   */

  n_args = _cogl_get_n_args_for_combine_func (b->texture_combine_rgb_func);
  for (i = 0; i < n_args; i++)
    {
      if (b->texture_combine_rgb_src[i] ==
          COGL_PIPELINE_COMBINE_SOURCE_CONSTANT)
        {
          /* XXX: should we be careful to only hash the alpha
           * component in the COGL_PIPELINE_COMBINE_OP_SRC_ALPHA case? */
          need_hash = TRUE;
          goto done;
        }
    }

  n_args = _cogl_get_n_args_for_combine_func (b->texture_combine_alpha_func);
  for (i = 0; i < n_args; i++)
    {
      if (b->texture_combine_alpha_src[i] ==
          COGL_PIPELINE_COMBINE_SOURCE_CONSTANT)
        {
          /* XXX: should we be careful to only hash the alpha
           * component in the COGL_PIPELINE_COMBINE_OP_SRC_ALPHA case? */
          need_hash = TRUE;
          goto done;
        }
    }

done:
  if (need_hash)
    {
      float *constant = b->texture_combine_constant;
      state->hash = _cogl_util_one_at_a_time_hash (state->hash, constant,
                                                   sizeof (float) * 4);
    }
}

void
_cogl_pipeline_layer_hash_user_matrix_state (CoglPipelineLayer *authority,
                                             CoglPipelineLayer **authorities,
                                             CoglPipelineHashState *state)
{
  CoglPipelineLayerBigState *big_state = authority->big_state;
  state->hash = _cogl_util_one_at_a_time_hash (state->hash, &big_state->matrix,
                                               sizeof (float) * 16);
}

void
_cogl_pipeline_layer_hash_point_sprite_state (CoglPipelineLayer *authority,
                                              CoglPipelineLayer **authorities,
                                              CoglPipelineHashState *state)
{
  CoglPipelineLayerBigState *big_state = authority->big_state;
  state->hash =
    _cogl_util_one_at_a_time_hash (state->hash, &big_state->point_sprite_coords,
                                   sizeof (big_state->point_sprite_coords));
}